Thermo-vibrational analysis of temperature dependent damping characteristics of viscoelastic materials

Viscoelastic materials like natural rubber (NR) and poly naphthalene sulphonate (PNS) are commonly used in damping and sealing applications. This study aimed to estimate their damping parameters using aluminum as the base material. The materials were prepared into an unconstrained sandwich beam, known as an Oberst beam, to assess their damping behavior under temperature variations. The beams were subjected to sinusoidal base excitation (1 g) over a frequency range of 20 Hz to 1000 Hz at temperatures of 40°C, 60°C, and 80°C. Notable behavior was observed at 40°C and 80°C, with both materials exhibiting good damping below 40°C and softening above 80°C. The 3 dB method was applied to estimate damping characteristics at the first three fundamental natural frequencies, with frequency response functions (FRFs) captured at the beam tip. While the first natural frequency showed minimal frequency shifts, the second and third natural frequencies revealed more pronounced changes in damping parameters, particularly for NR. Temperature increased the damping ratio and loss factor for both materials, indicating higher energy dissipation, while the quality factor decreased. NR exhibited significant reductions in damping efficiency at higher temperatures, especially at the second and third natural frequencies, whereas PNS showed more stable behavior. These findings suggest NR is ideal for high-damping applications at elevated temperatures, while PNS is better suited for stable damping across a wider temperature range.